Saw apparatus

ABSTRACT

Herein disclosed is a saw apparatus having circular saw blades which are independently axially movable on a rotary shaft supporting the blades for cutting a board to sections along markings applied on the face or faces of the board. The markings are sensed by a scanning arrangement and signals are produced when the scanning arrangement detects the markings. The saw blades are shifted to positions specified by these signals which represent the locations of the individual markings.

United States Patent 191 Ikeya et a1.

SAW APPARATUS Inventors: Akira lkeya; Hiroshi Ueno;

Toshiyuki Suzuki, all of Hamakita, Japan Assignee:

Nippon Gakki Seizo Kabushiki Kaisha, Hamamatsu-shi, Japan Filed:

Oct. 16, 1973 Appl. No.: 406,957

Related U.S. Application Data Continuation of Ser. No. 284,150, Aug 28, 1972,

abandoned.

Foreign Application Priority Data Aug. 17, 1971 Japan 46-77691 Aug. 27, 1971 Japan 46-77692 Aug 27, 1971 Japan 1. 46-66037 Aug. 27, 1971 Japan 4666038 Aug. 27, 1971 Japan 46-66039 Apr. 29, 1972 Japan 47-43001 U.S. Cl. 1. 83/365; 83/368; 144/312;

83/71; 83/425.4 Int. Cl B26d 5/34; 1327b 7/04 Field of Search 83/368, 425.4, 365, 157,

[111 3,885,483 451 May 27, 1975 [56] References Cited UNITED STATES PATENTS 1959,667 5/1934 Gran 1. 83/4254 2,877.846 3/1959 Tobey .1 83/365 1120861 2/1964 Finlay et alt... 83/365 3.276.492 10/1966 Kervefors 83/4254 3,811,353 5/1974 Miles 83/71 Primary Examiner-Donald R. Schran Attorney, Agent, or Firm-Hans Berman 5 7 ABSTRACT Herein disclosed is a saw apparatus having circular saw blades which are independently axially movable on a rotary shaft supporting the blades for cutting a board to sections along markings applied on the face or faces of the board. The markings are sensed by a scanning arrangement and signals are produced when the scanning arrangement detects the markings. The saw blades are shifted to positions specified by these signals which represent the locations of the individual markings.

14 Claims, 12 Drawing Figures PATENTEB HAYZ 71575 SHEET PATENTEU )IAY 2 7 I975 SHEET PATENTEJ KHZ H975 FIGBA SHEET 9 Q a 2 m N no no SAW APPARATUS This is a continuation of application Ser. No. 284,1 50, filed Aug. 28, 1972, and now abandoned.

The present invention relates to saw apparatus for use in lumber mill operations and, more particularly, to a saw apparatus having at least one circular saw blade which is axially movable on an arbor on which the saw blade is mounted.

While the saw apparatus herein disclosed may be of any of the types such as ripsaws, crosscut saws and miters, the present invention will be described as embod ied, by way of example, in ripsaw machines for cutting planks, boards or slabs, especially boards having knots or flaws.

For the purpose of preparing boards which are clear of knots or flaws, it is presently an ordinary practice that an operator marks the supplied board in volatile ink for identification of the objectionable knots or flaws and another operator then feeds the board to the ripsaw machine upon visual inspection of the marks to cut off the marked sections. Since, the board usually has two or more knots or flaws and is thus marked at two or more spots, it is necessary to have the board or cut section or sections of the board fed to the saw a number of times until all the knots are removed therefrom. The cut section or sections of the board must therefore be returned from the delivery side of the saw by a third operator usually by the use of a conveyor arrangement. At least three operators are thus required for the preparation of knotless or flawless boards in the lumber mill, resulting in unsatisfactory operation efficiency.

A ripsaw machine has therefore been proposed and put in practical use in which a plurality of saw blades are axially movable on an arbor positioned transversely to the direction of travel of the board. The saw blades are moved to align with the markings on the board to be cut so that the board is cut into sections all at a time along the markings. At least two operators are required to carry out this operation, one for marking the board and the other for feeding the board to the saw and positioning the saw blades in accordance with the given markings on the board. The operation efficiency is thus still unsatisfactory. Since, moreover, the saw blades are shifted by the use of a pushbutton arrangement, meticulous and time-consuming manipulation of the pushbuttom arrangement is indispensable for having the saw blades accurately positioned in compliance with the markings on the board.

It is, therefore, an important object of the present invention to provide an improved saw apparatus which is capable of preparing knotless or flawless boards at a satisfactorily enhanced operation efficiency.

It is another important object of the invention to provide an improved saw apparatus which is capable of cutting a board into two or more knotless or flawless sections in a completely automatized fashion in accordance with the markings preliminarily applied to the board for identification of the knots or flaws.

It is still another important object of the invention to provide an improved saw apparatus adapted to auto matically cut a board to sections with utmost accuracy in accordance with the markings on the board.

The object of the present invention will be advantageously accomplished in a saw apparatus which comprises a rotary shaft, at least one circular saw blade which is rotatable with and axially movable on the rotary shaft, conveying means for conveying the marked board in a predetermined path which is aligned with the saw blade or blades, light-sensitive scanning means operable for detecting the marking or markings on the board, signal generating means responsive to the scanning means for producing a signal representative of the location of each marking on the board, and saw-blade positioning or shifting means responsive to the signal or signals from the signal generating means for moving the saw blade or blades to a position or positions which are aligned respectively with the marking or markings whereby the board is cut into sections along the marking or markings. The conveying means may comprise board guiding means for guiding the board in the predetermined path which is transverse to the rotary shaft when the board is being passed through the lightsensitive scanning means and through the saw blade or blades. The conveying means may further comprise stop means associated with the light-sensitive scanning means for temporarily holding the board at a standstill when the board is being scanned by the scanning means. The saw-blade shifting means usually comprises driving means which is normally operative, control means responsive to the signal or signals from the signal generating means for actuating the drive means, and transmitting means for transmitting mechanical power from the driving means to the saw blade or blades. The light-sensitive scanning means may be constructed in any desired manner but, in the preferred embodiment which is to be described, such means is adapted to be moved relative to the board and to respond to the marking or markings on the board. Thus, the lightsensitive scanning means may comprise a carrier which is movable over the path of the board in a direction transverse thereto, a source of light to irradiate the board to be scanned, a plurality of photoelectric elements stationary on the carrier, driving means for moving the carrier in the aforesaid direction, and switching means for controlling the movement of the carrier relative to the board. Where the light-sensitive scanning means is constructed in this manner, the signal generating means may comprise gearing means responsive to the movement of the carrier of the scanning means, at least one mark-position indicative potentiometer responsive to the motion of the gearing means for producing a signal voltage which is indicative of the location of each marking on the board, uncoupling means for disconnecting the potentiometer from the gearing means when the marking on the board is detected by the light-sensitive scanning means, at least one bladeposition indicative potentiometer responsive to the axial movement of the associated saw blade for producing a signal voltage indicative of the instantaneous position of the saw blade on the rotary shaft, and comparing means for comparing the signal voltages from the mark-position and blade-position indicative potentiometers for producing an output voltage which is proportional to the difference between the signal voltages from the potentiometers. In this instance, the control means of the saw-blade shifting means may comprise valve means which is responsive to the output signal from the comparing means of the signal generating means so that the associated saw blade is moved in a manner to reduce or increase the signal voltage from the bladeposition indicative potentiometer and accordingly vary the output voltage from the comparing means to zero.

The conveying means includes a conveyor such as a caterpillar conveyor which is positioned in association with the saw blade or blades so that the board is conveyed thereon in a direction transverse to the rotary shaft carrying the saw blade or blades. It is, in this instance, preferably that the conveying means further includes elastic pressing means adapted to elastically press the board or the cut sections of the board upon the conveyor and to accordingly enable the board or cut sections to advance in a stabilized condition while the board is being fed to the saw blade or blades or the cut sections of the board are leaving the saw blade or blades. The individual cut sections of the board usually have reduced widths and, as a consequence, a difficulty may be encountered in stably retaining the cut sections between the pressing means and the conveyor especially where the supplied board has a thickness varying widthwise of the board. This difficuty will be eliminated through provision of first and second sets of rollers which are positioned anterior and parallel to the rotary shaft mounting the saw blade or blades and a plurality of spring means which are operable to respectively press the rollers against the individual cut sections of the board which are being conveyed away from the saw blade or blades. The rollers of each set are aligned with and axially spaced from each other and, furthermore, the first and second sets of rollers are disposed alternately from each other and partly coextensively at their axial end portions.

To prevent the board from being moved backwardly from the saw or blade or blades by the rotary action of the blade or blades, return-preventive means in a suitable form may be positioned anterior to the saw blade or blades and in association with the pressing means. The position of the pressing means relative to the conveyor underlying the saw blade or blades may be adjusted to meet the thickness of the board through provision of suitable adjusting means.

The saw blade or blades are usually encased in a suitable housing and, thus, it is difficult, if not impossible, visually to inspect the saw blade or blades from the outside of the apparatus during operation. To enable the operator (or the marker) to visually confirm the movement of the saw blade or blades, there may be provided saw-blade position indicating means which cooperate with the saw-blade shifting means.

The saw apparatus having the general construction above described may further comprise preliminary conveying means which is adapted to completely automatize the sawing operation using the saw apparatus. The preliminary conveying means is associated with the main conveying means and is thus operable to supply the marked boards to a starting end of the main conveying means from the marking station. In one preferred form, the preliminary conveying means comprises a conveyor adapted to move the marked board in a direction substantially transverse to the path of the board to be carried on the main conveying means, stop ping means for stopping the preliminary conveying means when the board carried thereon is brought into alignment with the direction of movement of the main conveying means, and transfer means for passing the board from the preliminary to the main conveying means when the preliminary conveying means is stopped.

The features and advantages of the saw apparatus according to the present invention will become more ap parent from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a plan view showing an overall construction of the saw apparatus embodying the present invention;

FIG. 2 is a longitudinal sectional view showing in a schematic form the saw-blade shifting meachanism of the saw apparatus illustrated in FIG. 1;

FIG. 3 is a cross sectional view showing on an enlarged scale the saw-blade guiding arrangement of the shifting mechanism illustrated in FIG. 2;

FIG. 4 is a perspective view showing a shifter forming part of the shifting mechanism of FIG. 2;

FIG. 5 is an end view showing relative positions of some essential parts and elements of the shifting mechanism;

FIG. 6a is a cut-away view showing partly in vertical section the board feeding and delivery mechanisms for the circular saw unit of the apparatus according to the present invention;

FIG. 6b is also a cut-away view showing, now partly in horizontal section, the feeding and delivery mechanisms of FIG. 6a;

FIG. 7a is a schematic plan view of the blade-position indicating arrangement of the saw apparatus shown in FIG. 1;

FIG. 7b is a front end view of an indicator panel forming part of the blade-position indicating arrangement of FIG.

FIG. 8 is a plan view showing, on an enlarged scale, a modified form of light-sensitive scanning and signal generating arrangements to be incorporated in the saw apparatus according to the present invention;

FIG. 9a is a schematic circuit diagram of a preferred example of the signal generating arrangement of the saw apparatus; and

FIG. 9b is a schematic view showing part of the signal generating arrangement and the control arrangement of the blade shifting mechanism of the saw apparatus of the present invention.

Reference will now be made to the drawings, first to FIG. 1 in which the overall construction of the saw apparatus in a preferred form is illustrated.

As previously discussed, the saw apparatus herein proposed is specifically adapted to cut wood boards into sections which are cleared of knots or flaws in a completely automatized fashion and with utmost accuracy. The boards, designated by reference numeral 10, are thus successively supplied from a board marking station (not shown) at which markings m are applied to the boards to identify the locations of the knots or flaws k, if any, on the boards. A suitable preliminary conveying arrangement 12 is adapted to pass the marked boards 10 to a light-sensitive scanning and signal generating arrangement 14 which detects and memorizes the locations of the markings m on the boards 10. The boards 10 are then fed through an intermediate transfer mechanism 16 to a sawing unit 18 which is positioned over a board feeding and delivery arrangement 20. The sawing unit 18 is associated with a saw-blade positioning or shifting mechanism 22 which is operable to move the saw blades of the unit in accordance with the signals from the scanning and signal generating arrangement 14. A blade-position indicating arrangement 24 cooperates with the blade shifting mechanism so as to visually indicate the positions of the saw blades for permitting the operator to monitor the operation of the sawing unit 18.

The preliminary conveying arrangement 12 includes an endless belt conveyor 26 which is driven to move the marked boards in a predetermined direction which is usually transverse to the path of the boards to the sawing unit 18. A rail 28 serving as a stop member is positioned transversely to the direction of travel of the belt conveyor 26 and carries thereon a limit switch 30 which is adapted to be actuated when the board l0 strikes against the stop member 28 and is thus brought to a standstill on the conveyor 26. A pneumatic of hydraulic cylinder 32 has a plunger 320 which is extendible across the entire width of the belt 26. Both the conveyor 26 and cylinder 32 coact with the limit switch 30 so that, when the limit switch is actuated, the conveyor 26 stops and the plunger 32a of the cylinder 32 is extended from its retracted position whereby the board 10 bearing against the stop member 28 is passed over to the succeeding station. The plunger 32a of the cylinder 32 is then withdrawn to its initial position until it presses a limit switch 34 which is carried on the cylinder 32.

The board 10 which has thus left the conveyor 26 is now moved on a main conveying mechanism including a conveyor 36 and an associated guide rail 38. The conveyor 36 and guide rail 38 are adapted to guide the board 10 in a direction which is transverse to the direction of travel of the preliminary conveyor 26 and to the axis of rotation of the saw blades of the sawing unit 18 to be descried later. The guide rail 38 is integral with the stop member 28 of the preceding conveying station. A pressing rod 40 is biased by a spring to rotate about its pivot toward the guide rail 38 and thus presses the board 10 against the guide rail 38 when the board passes between the rail 38 and pressing rod 40, as illustrated.

The conveyor 36 may be positively driven from a suitable driving source or, where desired, may not be driven positively. If, thus, the conveyor 36 is not positively driven, then an arrangement may be provided so that the board 10 carried on the conveyor is moved foreward by means of a succeeding board which is moved from the preliminary conveyor 26 by the plunger 32a of the pneumatic or hydraulic cylinder 32. Where, moreover, it is desired that the board 10 be marked on both sides thereof, the conveyor 36 may be constituted as a roller conveyor as illustrated so that the markings on both faces of the board can be detected.

At the forward end of the conveyor 36 are positioned gate members 42 and 42 which are adapted to be raised and lowered through the upper level of the conveyor 36 by suitable driving means (not shown). When, thus, the gate members 42 and 42' are in the raised positions, the board It) bears at its forward end against these members and is consequently held at a standstill on the conveyor 36 as illustrated. The gate members 42 and 42' are controlled by the previously mentioned limit switch 30 and are thus raised when the switch 30 is actuated and accordingly the board 10 is transferred from the preliminary conveyor 26 to the main conveyor 36.

When the board 10 is thus held at rest on the conveyor 36, then the light-sensitive scanning and signal generating arrangement 12 is initiated into action so as to produce signals representative of the locations of the markings m on the board. The scanning and signal generating arrangement 14 is controlled by a limit switch 44 which is located at the forward end of the conveyor 36. The limit switch 44 is adapted to be actuated when pressed upon by the board 10 reaching the forward end of the conveyor 36 and thus held at a standstill by the gate members 42 and 42. This limit switch 44 is also associated with the cylinder 32 of the preliminary conveying arrangement 12 so that the plunger 32a of the cylinder 32 is withdrawn from its fully projecting position when the limit switch 44 is actuated.

The ligh sensitive scanning and signal generating arrangement 14 includes a carrier 46 which carries thereon a plurality of lights 46a and a plurality of photo-electric elements 46b which are uniformly spaced from each other. The photo-electric elements 460 per se are well known in the art, producing signal voltages which are proportional to the intensities of the light incident thereon from the surface of the board 10 which is irradiated with the light from the light sources 46a. The carrier 46 is mounted on spaced guide bars 48 and 48' having rollers 50 and 52', respectively, and is thus movable transversely to the direction of travel of the board 10, viz., to the guidrail 38, across the conveyor 36. The carrier is driven by suitable driving means such as for example a pneumatic or hydraulic cylinder 52 having a piston which extends transversely to the carrier 46. This piston of the cylinder 52 is integral with or rigidly connected to a toothed bar or rack 54 which forms part of a mark-position signal generator. The mark-pt. sition signal generator, generally designated by reference numeral 56, includes a support 58 carrying thereon a desired number of pinions 60 which are in mesh with the bar 54. The number of the pinions 60 is equal to the number of the cutting elements of the sawing unit 18. The sawing unit 18 is herein assumed by way of example to have four saw blades as will be described later and four pinions 60 are used in the embodiment illustrated. The pinions 60 are respectively connected with potentiometers 62 through shafts 64. These potentiometers 62 produce voltages proportional to the angles of rotation of the pinions 60 on the bar 54 and are disconnected by suitable uncoupling means such as clutches 66 positioned intermediate the pinions 60 and potentiometers 62 when associated photo-electric elements 46b on the carrier 46 detect the markings m on the board 10, as will be described in more detail. The clutches 66 are preferably provided with brakes (not shown) which are adapted to positively stop the rotation of the associated potentiometers 62 when the potentiometers are uncoupled from the pinions 60. The clutches and the associated brakes are usually of the solenoid actuated types. Designated by reference numeral 68 are torque limiters which are preferably connected between the pinions 60 and clutches 66.

Limit switches 70 and 72 are positioned at the ends of the path of the carrier 46. The limit switch 70 remote from the guide rail 38 is actuated to return the carrier 46 to the initial position close to the guide rail 38 when engaged by the carrier 46. This limit switch 70 is further operable to lower the gate members 42 and 42' and to uncouple the clutch or clutches 66 which are kept coupled when the carrier 46 reaches the position farthest from the initial or rest position. The limit switch 72, on the other hand, is responsive to the return of the carrier 46 and holds it in the rest or inoperative position until the limit switch 44 is actuated for a second time.

While the carrier 46 is thus moved across the board resting on the conveyor 36, the photo-electric elements 46b sense the markings m on the board 10 so that the potentiometers 62 produce signals repr sent-ative of the locations of the markings. Upon completion of the scanning operation, the limit switch is actuated and accordingly the gate members 42 and 42' are lowered, thereby permitting the board I" on the conveyor 36 to be advanced by the positive) riven conveyor 36 or by the succeeding board being moved from the preliminary conveyor 26. The board 10 is thus passed to the intermediate transfer mechanism 16.

The intermediate transfer mechanism 16 forms part of the main conveying arrangement and includes a plurality of spaced rollers 74 which are driven by a driving motor 76 through a reduction gearing 78 and a cou pling 80 as is customary. The transfer mechanism 16 in its entirety may be preferably to positioned as to have the board 10 constantly pressed upon the guide rail 38. The board 10 leaving the transfer mechanism 16 is now conveyed on a suitable type of conveyor such as a caterpillar conveyor 82 which also forms part of the main conveying arrangement of the saw apparatus according to the present invention. The conveyor 82 is driven by a driving motor 84 through non-illustrated reduction gearing for feeding the board 10 to the sawing unit 18. Designated by reference numeral 86 is a lubricating arrangement for the conveyor.

The board 10 thus fed to the sawing unit 18 is cut into sections by blades which are moved to positions selected in accordance with the signals from the potentiometers 62 of the mark-position signal generator 56. To prevent the saw blades of the unit 18 from being shifted during the cutting operation, sensors 88 and 88' and 90 and 90 may preferably be provided which are responsive to the presence and absence of the board on the sawing unit. Such sensors may be of the type using photo-electric elements.

The sawing unit 18 and the associated saw-blade shifting mechanism 22 are illustrated in FIGS. 2 and 3. As seen in FIG. 2, the sawing unit is carried on a rotary shaft 92 which is rotatable on a casing 94 in bearings 96, 98 and 100. The rotary shaft 92 is driven by a grooved pulley 102 and beltings 104. A pair of outer collars 106a and 106d and a pair of inner collars 10Gb and 1060 are axially moved on the shaft 92 by guiding means which are to be described later. The outer col lars 106a and 106d have flange portions extending toward each other and spaced from the rotary shaft 92. The flange portions of the outer collars 106a and 106d have inner peripheral surfaces engageable with outer peripheral surfaces of inner collars 1061: and 1060, respectively. Likewise, the inner collars 10617 and 1066 have flanges or annular projections which are engageable with the leading ends of the cylindrical flanges of the outer collars 106a and 106d, respectively. The collars 106a to 106d carry on their flange portions circular saw blades 1080 to 1080', respectively, which are thus movable with the associated collars in an axial direction on the shaft 92 and independently of each other. Four saw blades 1080 to 108d are herein shown by way of example. It is, however, apparent that the number of the saw blades can be increased or decreased as desired depending upon requirements. The collars 106a to 106d are splined or keyed as at 110 in FIG. 3 to the shaft 92 so as to rotate therewith when the shaft is driven.

The rotary shaft 92 is formed with at least four circumferentially spaced grooves 112 having enlarged bottoms as seen in FIG. 3 and axially extending from one end of the shaft 92 to the other. Guide rods 114 are conformingly received in of the grooves 112, longitudinally slidable in these grooves and secured respectively at one end to the collars 106a to 106d through a pin or pins 116, as seen in FIG. 3. Designated by reference numeral 118 are retainers for holding the pin or pins 116 in position.

Each of the guide rods 114 is connected at the other end to a sleeve 120 which is axially slidable on the rotary shaft 92 out of range of the conveyor 82, as seen in FIG. 2. A ring 124 having an annular extension 1240 is rotatable on this sleeve 120 through a bearing 126, the ring 124 being prevented from moving axially on the sleeve 120. This ring 124 is moved by means of a shifter 128 which is slidable on a guide shaft 130 parallel to the rotary shaft 92 and supported on the casing 94. The construction of the shifter 128 is more clearly seen in FIG. 4. Referring thus to FIG. 4, the shifter 128 has a sleeve portion 132 which is axially slidable on the guide shaft 130 and a fork or a pair of lower arms 134 and 134' which override the ring 124 (FIG. 2). The spaced lower arms 134 and 134' have lower ends portions 136 and 136', respectively, which are in engagement with the annular extension 124a of the ring 124. These portions 136 and 136' are herein illustrated as constituted by claws which have notches 138 and 138' adapted to grasp the annular extension 124a of the ring 124. These claws may be formed integrally with the arm portions 134 and 134 or may be bolted or welded thereto where desired. The shifter 128 further includes an upper projection 140 which is substantially diametrically opposed to the lower arm portions 134 and 134. This upper projection 140 is connected to a piston rod 142 of a hydraulic cylinder 144 through an adjustable and cushioning joint 148. The hydraulic cylinder 144 communicates with a source of a pressurized fluid through a suitable solenoid operated valve 146 which is controlled in a manner to be described later.

The sleeve 120, ring 124, shifter 128 and cylinder 144 are provided on each of the guide rods 114 and accordingly on each of the saw blades 1080 to 108a and, thus, the four independent mechanical linkages interconnecting the collars 1060 to 106d and the four cylinders 144 constitute the saw-blade shifting mechanism of the saw apparatus according to the present invention. More particularly, the sleeves 124 and associated rings 124 are positioned in series with each other on the rotary shaft 92 while the shifters 128, guide shafts 130 and cylinders 144 are disposed substantially concentrically with respect to the rotary shaft 92 as will be understood from FIG. 5 in which the positions of the guide shafts now designated by 130a to 130d and cylinders now designated by 1440 to 144d relative to the saw blades commonly designated by 108 are illustrated.

The saw-blade shifting mechanism of the construc tion above described is operatively associated with the signal generating arrangement for controlling the blade shifting operation of the shifting mechanism in accordance with the signal or signals indicative of the location or locations of the markings on the board to be cut as previously mentioned. Thus, in the embodiment shown, a toothed rack 150 is connected at one end to the upper projection 140 of each of the shifters 128, extending substantially in parallel to the shafts 92 and 130 an longitudinally movably supported on the casing 94 as seen in FIG. 2. The rack 150 is in constant mesh with a pinion 152 which is rotatable on a shaft 154 carried on the casing 94 through a bracket 156 positioned externally of the casing. This shaft 154 is rotatable with a blade-position indicating potentiometer 158 which is adapted to produce a signal voltage proportional to the angle of rotation of the pinion 152 on the rack 150. A rack 150, pinion 152, shaft 154 and potentiometer 158 are associated with each of the shifters 128 and saw blades 108 and angularly offset with respect to the rotary shaft 92. This will be clearly seen in FIG. 5, in which the relative positions with respect of the saw blades 108 of the racks, pinions, shafts and potentiometers all designated with numerals with subscripts a, b. c and d to correspond to the associated guide shafts 1300, 130b, 1306 and 130d, respectively, are illustrated.

As illustrated in block form in FIG. 2, the markposition indicating potentiometer 62 and the bladeposition indicating potentiometer 158 for each of the saw blades are connected in parallel to a comparator 160 for controlling the solenoid operated valve 146 as will be described in more detail. The mark-position indicating potentiometer produces a signal voltage which is proportional to the distance of the marking m on the board from the edge of the board close to the rest position of the carrier 46 of the light-sensitive scanning mechanism (see FIG. 1). The potentiometer 158 is adapted to produce a signal voltage which is propor tional to the distance of the associated saw blade from the resting position thereof. These signal voltages are fed to the comparator 160 the saw blade is moved until the difference between the voltages from the potentiometers 62 and 158 becomes zero.

FIGS. 6a and 6b illustrate a preferred construction of the board feeding arrangement 22 which largely consists of a mechanism 22a for feeding the board 10 to the sawing unit and a mechanism 221) for delivering the cut sections 10a, 10b, 100 (FIG. 1) of the board 10 from the sawing unit. The board feeding and delivery mechanisms 22a and 22b, respectively, are accommodated within a casing 162 which includes reinforcement plates 162a and 16212. The board feeding mechanism 220 is positioned anterior to the sawing unit having saw blades 108 and serves to press the board 10 against the conveyor 82 while the board is advancing toward the saw blades 108.

The board feeding mechanism 22a starts with a return-preventive member 164 which is swingable over the conveyor 82. The return-preventive member 164 is attached to a pivotal member 166 which is journaled on the casing 162 and biased to turn in a direction to press the return-preventive member 164 against the board 10 being passed thereunder. The pivotal member 166 is biased by a helical spring 170 which is anchored to the rear end portion of the casing 162. The pivotal member 166 carries thereon an abutment 172 which is engageable with a stop member 174 projecting rearwardly of the casing 162 in alignment with the abutment 172. The pivotal motion of the return-preventive member 164 on the pivotal member 166 is thus limited by abutting engagement of the abutment 172 with the stop member 174 so that rearward movement of the board 10 past the return-preventive member 164 is prevented. A cross shaft 176 is positioned anterior to or ahead of the sawing unit and parallel to the rotary shaft carrying the saw blades 108. The shaft 176 is supported at its opposite ends on the casing 162 as seen in FIG. 6b. Arms 178 and 180 are pivotally mounted on this cross shaft 176, respectively extending rearwardly and forwardly of the shaft 176. At the free end portions of these arms 178 and 180 are mounted main pressing rollers 182 and 184 on shafts 182a and 184a, respectively, which are parallel to the cross shaft 176 and movable relative to the casing 162. The pressing rollers 182 and 184 are thus not only rotatable about the shafts 182a and 1840 but are turnable about the cross shaft 176 on the arms 178 and 180, respectively. The rearward pressing roller 182 is biased downward by means of helical compression springs 186 which are seated at their lower ends on pressing plates 188 resting on the top of the roller 182 and at their upper ends on spring seat plates 190 supported by adjusting bolts 192 which are fastened to the top wall of the casing 162 by nuts 194. Likewise, the forward roller 184 is urged downward by compression springs 196 which are seated between pressing plates 198 and spring seat plates 200. These spring seat plates 200 are also secured to adjusting bolts 202 fastened to the casing 162 by nuts 204. Designated by reference numerals 206 and 208 are stop members for the arms 178 and 180 which are rockable about and on both sides of the cross shaft 176.

Between the forward pressing roller 184 and the sawing unit is positioned another cross shaft 210 parallel to the first cross shaft 176 and supported on the side walls of the casing 162. The cross shaft 210 carries an arm 212 for an auxiliary pressing roller 214 which is positioned adjacent the sawing unit as seen in FIGS. 6a and 6b. The cross shaft 210 also carries a generally upwardly extending arm 216 which moves together with the arm 212 about the shaft 210. The upright arm 216 has mounted at its uppermost portion a pivotal shaft 218 on which one end of an adjusting rod 220 is journaled. The adjusting rod 220 extends over the main pressing rollers 182 and 184 rearwardly of the arm 216 and projects outwardly of the rear end wall of the easing 162. The adjusting rod 220 is biased forwardly by means of a compression spring 222 which is seated at its forward end on a spring seat member 224 secured to the rod 220 and at its rearward end on the rear end wall of the casing 162. Where desired, the adjusting rod 220 may be screwed at its outer end portion to an adjusting nut 226 so that the length of the adjusting rod 220 extending within the casing 162 may be varied. The cross shaft 210 is further provided with a returnpreventive member 228 which pivots on the shaft 210 in the direction of the path of the board 10 to be conveyed thereunder. The return-preventive member 228 has a lower portion directed generally dowwardly for contact with the board 10 and an upper portion which is directed generally upwardly and rearwardly. This upper portion of the return-preventive member 228 is engageable at its free end with a stop member 230 which is fast on the casing 162. The return-preventive member 228 permits movement of the board 10 on the conveyor 82 toward the sawing unit but prevents the board from being moved rearwardly, similarly to the return-preventive member 164 located upstream thereof.

The delivery mechanism 22b, on the other hand, is positioned after or behind the sawing unit and thus serves to feed the cut sections of the board to a storage station (not shown) succeeding the saw apparatus. The delivery mechanism 22b includes a cross shaft 232 parallel to the rotary shaft for the saw blades 108 and supported on the side walls of the casing 162. The cross shaft 232 carries thereon a first set of arms 234 and a second set of arms 236. The arms 234 and 236 of the two sets are juxtaposed alternately and extend rearwardly from the cross shaft 232 toward the saw blades 108. The arms 234 are shorter than the arms 236. The arms 234 and 236 carry on their downwardly bent end portions pressing rollers 238 and 240 respectively which press upon and roll on the cut sections of the board on the conveyor 82. The rollers 238 have a common axis and are axially spaced from each other. Likewise, the rollers 240 are axially spaced from each other and have a common axis which is parallel to the axis of the first set of pressing rollers 238 and accordingly to the cross shaft 232. The pressing rollers 238 have end portions coextensive with the end portions of the press ing rollers 240 so that the roller arrangement in its entirety extends over the entire width of the conveyor 82. The cross shaft 232 further carries a plurality of generally upwardly extending arms 242 which are integral with respective arms 234 and 236. These upright arms 242 have pivot pins 244 at their uppermost portions, and adjusting rods 246 are connected by the pins to the arms 242. The adjusting rods 246 are biased rearwardly by means of compression springs 248 which are seated on spring seat members 250, as seen in FIG. 6b. The ad justing rods 246 project beyond the forward wall of the casing 162 and are provided with adjusting nuts 252 which are connected to the threaded outer end portions of the rods 246.

Behind the cross shaft 232 is positioned a pressing roller arrangement which is similar to the roller arrangement of the board feeding mechanism 220. The pressing roller arrangement of the delivery side thus includes a cross shaft 254 supported on the side walls of the casing 162. The cross shaft 254 pivotally carries at its opposite end portions rearwardly and forwardly extending arms 256 and 258, respectively. The arms 256 and 258 carry at their free end portions pressing rollers 260 and 262, respectively. These pressing rollers 260 and 262 are urged downward by spring means which are carried on the top wall of the casing though not shown so that the rollers are depressed against the cut sections of the board 10 fed from the sawing unit. Designated by reference numerals 264 and 266 are stop members for the arms 256 and 258.

The vertical position of the entire roller arrangement making up the board feeding and delivery mechanisms 22a and 221) can be varied by a position adjusting mechanism which is designated generally by reference numeral 268. The position adjusting mechanism 268 includes a stationary bracket 270 which supports a shaft 272 extending therethrough. The shaft 272, in turn, supports at one end thereof a wheel 274 rotatable with the shaft and at the other end a bevel gear 276. The gear 276 is in constant mesh with a bevel gear 278 on a lifting column 280 supported on the top wall of the casing 162. The lifting column 280 is screwed to a screw bearing 182 positioned within the casing 162. The casing 162 and all the parts and elements supported thereon are thus moved upwardly or downwardly through manipulation of the wheel 274.

Designated by reference numeral 283 in FIG. 6a is a semi-cylindrical hood for the sawing unit. The hood 283 is provided with a saw-dust discharge duct 285 which extends outwardly of the casing 162 through, for

5 example, the top wall of the casing 162 as illustrated. FIGS. 7a and 7b illustrate a preferred construction of the saw-blade position indicating arrangement which is designated generally by the reference numeral 24 in FIG. 1 and part of which is seen in FIG. 4. Referring thus to FIGS. 4, 7a and 7b, the blade-position indicating arrangement includes four flexible lines 284 which are connected each at one end to the upper extensions 140 of the shifters 128 (FIG. 4). The flexible lines 284 may be actually ropes, wires, cables or chains. The flexible lines 284 are first passed in a direction parallel to the rotary shaft 92 of the saw blades 108 and are then turned laterally over respective guide rollers 286. The lines are next turned at right angles toward the supply side of the sawing unit over respective guide rollers 288 and are further turned back through respective guide rollers 290. The guide rollers 286, 288 and 290 are carried on a suitable stationary structure. These guide rollers 286 should be replaced with sprocket wheels where it is desired that the chains are used as the flexible lines. The flexible lines 284 are connected to spring retainers 292 movable within a frame structure 294 in a direction parallel to the rotary shaft 92 of the sawing unit. Springs 296 are connected each at one end to these spring retainers 292 respectively and at the other to the side wall of the frame structure 294, thereby urging the flexible lines 284 in the directions of arrows in FIG. 7b. The spring retainers 292 are integral with or connected to guide pins 298 which are slidable in spaced elongated slots 300 formed in a front wall of the frame structure 294 as seen in FIG. 7b. Movable with these guide pins 298 are indicator rods 302 which extend in front of the supply side of the sawing unit. The indicator rods 302 support at their leading ends indicator elements 304 which are located and movable respectively in correspondence with the associated saw blades 108.

The operation of the saw apparatus which is constructed in a manner thus far described will now be explained with concurrent reference to FIGS. 1 to 7b.

When the board 10 having markings m identifying the knots or flaws k to be removed is brought into abutting engagement with the stop member or rail 28, then the limit switch is actuated so as to stop the preliminary conveyor 26 and cause the plunger 32a of the pneumatic or hydraulic cylinder 32 to project forwardly. The marked board 10 is accordingly moved by the plunger 32a to the roller conveyor 36 under the carrier 46 of the light-sensitive scanning arrangement. The advancement of the board 10 on the roller conveyor 36 is blocked by the gate members 42 and 42' which are in the raised condition. When the board 10 strikes against the gate members 42 and 42', it presses the limit switch 70 which causes the plunger 32a of the cylinder 32 to withdraw to its retracted position and the piston of the cylinder 52 to project. The carrier 46 supporting the lights 46a and photo-electric elements 46b is accordingly moved from its rest position, thereby scanning the marked face of the board 10 resting on the roller conveyor 36. The rack 54 is moved as the carrier 46 is thus moved away from the guide rail 38 so that the pinions 60 meshing with the rack 54 are rotated with the associated potentiometers 62 through the shafts 64 and clutches 66. When the photo-electric elements 46b on the carrier 46 thus moved transversely over the marked board sense the first marking on the board, then the first clutch 66 is uncoupled and the brake thereof is actuated to stop the associated potentiometer 62, which thus memorizes the location of the first marking on the board in the form of a voltage. As the second and third markings on the board are sensed by the photo-electric elements 46b on the carrier 46, the second and third potentiometers 62 are stopped in succession to memorize the locations of the markings. If three or fewer markings are present on the board 10, then one or more of the potentiometers 62 will remain connected to the associated pinions 60 until the carrier 46 and accordingly the rack bar 54 are moved throughout their full strokes. When, however, the carrier 46 reaches a position remotest from its rest position, he limit switch 70 is actuated so as to uncouple the clutches 66 associated with the potentiometers 64 which were kept connected to the pinions 60. The limit switch 70 also causes the piston rod of the cylinder 52 to withdraw for moving the carrier 46 to its rest position and the gate members 42 and 42' to be lowered below the level of the roller conveyor 36. The carrier 46 depresses the limit switch 72 when it reaches the rest position and is thereby held stationary cycle of op eration. Simultaneously, the plunger 32a of the cylinder 32 is withdrawn to the retracted position so as to be ready for moving a subsequent board to the scanning station.

The signal voltages produced by the potentiometers 62 of the signal generator unit 56 are fed to the comparators 160 (FIG. 2) for comparison with the signal voltages supplied from the potentiometers 158. Control signals are fed from the comparators 160 to the solenoid operated control valves 146 associated respectively with the saw blades 108 of the sawing unit. The control valves 146 then operate to move the piston rods 142 of the hydraulic cylinders 144 in a manner to equalize the voltages of the signals from the potentiometers 62 and 158, as will be described in more detail.

The shifters 128 are thus driven to slide on the respective guide shafts 130, thereby moving the associated sleeves 120 axially on the rotary shaft 92. This causes the collars 1060 to 106d of the sawing unit to axially slide on the rotary shaft 92. The saw blades 1080, 108b, 1086 and 108a or some of them are consequently moved over distances which are in agreement with the differences between the voltages supplied from the potentiometers 62 and 158. The movement of each saw blade is fed back to the associated potentiometer 158 through a mechanical linkage including the collar, guide rod 114, sleeve 120, ring 124, shifter 128, rack 150 and pinion 152 and thus varies the signal voltage from the potentiometer 158. The saw blades are consequently brought to a standstill when the differences between the signal voltages from the potentiometers 62 and 158 are eliminated. The saw blades are shifted while the shaft 92 is being rotated. The saw blades are in this manner shifted to positions which are aligned with the markings m on the board 10 leaving the lightsensitive scanning arrangement.

The sensors 88, 88', 90 and 90' located adjacent the sawing unit detect the presence or absence of a board on the sawing unit. In the absence of a board on the sawing unit, the sensors issue signals to allow the passage of the board 10 from the roller conveyor 36 to the conveyor 82 through the intermediate transfer mechanism 16 along the guide rail 38. The board 10 to be cut thus flaps the return-preventive member 164 upwardly and enters the board feeding mechanism 22a. While being conveyed on the conveyor 82 toward the sawing unit, the board 10 is held between the conveyor 82 and the pressing rollers 182 and 184 by the compression springs 186 and 196, irrespective of the variation in thickness or of the irregular thickness of the board 10. The uoard 10 then turns the second return-preventive member 228 and is fed to the saw blades 108 by the auxiliary pressing roller 214. The board 10 is thus cut into sections along the markings m on the board by the saw blades 108 which are shifted to the selected positions previously mentioned. The cut sections of the board, as designated by reference numerals 10a, 10b and 10c in FIG. 1, are passed away from the sawing unit while being pressed upon by the split pressing rollers 238 and 240 and further by the main pressing rollers 260 and 262 of the delivery mechanism 22b.

The solenoid operated clutches 62 of the signal generator unit 56 are again engaged upon completion of the shifting operation by the blade shifting mechanism and, as a consequence, the potentiometers 62 are rotated together with the associv' d pinions 60 in reverse directions as the carrier 4 is returned to the rest position whereby the potentiometers 62 are restored to the zero positions.

As the shifters 128 are moved during the saw-blade shifting operation as above described, the flexible lines 284 connected respectively thereto are moved in the direction of arrows in FIG. 7a by the actions of the tension springs 296, and the guide pins 298 are moved through the elongated slots 300 in the frame structure 294. The indicator elements 304 positioned at the rear of the sawing unit are, therefore, moved in synchronism with the saw blades 108 being shifted, thereby premitting visual inspection of the movements of the saw blades by the operator.

Although it has been described that the board 10 to be cut is brought to a standstill on the roller conveyor 36 when it is to be scanned by the photo-electric elements 46b on the carrier 46, the board 10 may be scanned while it is advancing toward the subsequent station where desired. The number, locations and timings of actuation of the switch elements and sensors in the saw apparatus above described may be selected depending upon operation requirements. Likewise, the numbers of the saw blades and potentiometers, and the parts and elements associated therewith, may be varied as desired. The potentiometers may be replaced by suitable computing means which are capable of providing information indicative of the number and locations of the markings on the board to be cut. The signal generator unit of the light-sensitive scanning and signal generating arrangement 14 may be modified in numerous manners where desired. FIG. 8 illustrates an example of such modifications of the scanning and signal generating arrangement. The signal generator unit above described must be kept inoperative for memorizing the locations of the markings of subsequent board until the saw-blade shifting operation is completed. This will apparently result in considerable loss in the performance efficiency of the sawing operation.

To eliminate this inconvenience, the signal generator unit shown in FIG. 8 uses two sets of potentiometers which are alternately put into operation. In FIG. 8, the parts and elements which correspond to those previously mentioned and illustrated are designated by like reference numerals and no detailed description thereof will be given.

Referring to FIG. 8, the modified signal generating unit includes a suitable number of pinions 60 which are in constant mesh with a rack 54 movable with the carrier 46 carrying the lights 46a and photo-electric elements 46b. Each pinion 60 is connected with two potentiometers 62 and 62 through solenoid operated clutches 66 and 66', respectively, having brakes adapted to positively stop the associated potentiometers when disengaged. Couplings 306 and 306' connect the clutches 66 and 66' with the associated potentiometers 62 and 62', respectively, and couplings 308 and 308' connect the clutches 66 and 66', respectively, with the associated pinions 60 through torque limiters 68.

When, in operation. the board 10 strikes the limit switch 44 and is brought to a full stop, then the carrier 46 starts to travel from its rest position for scanning the marked face of the board. In this instance, either of the two sets of potentiometers 62 and 62 is connected to the pinions 60 on the rack 54 so that, as the carrier 46 moves over the board 10, the rotation of the pinions 60 is imparted to, for example, the potentiometers 62 with the other set of potentiometers 62 kept disconnected from the pinions 60. The potentiometers 62 accordingly produce signal voltages which are proportional to the angles of rotation of the associated pinions 60. The solenoid operated clutches 66 are disengaged as the photo-electric elements 46!) on the carrier detect the markings on the board 10 for disconnecting the associated potentiometers 62 from the pinions 60. The potentiometers 62 are thus brought to a standstill by the action of the brakes attached to the clutches 66 and memorize the locations of the markings detected. The clutches 66 remaining in the engaged condition until the carrier 46 has moved through its full stroke are disengaged when the carrier strikes the limit switch 70. The carrier 46 then returns to its rest position and concurrently the board 10 on the conveyor 36 advances to the subsequent cutting station. While the board 10 is thus being transferred to the sawing unit, the saw blades of the sawing unit are shifted one by one in accordance with the signal voltages from the potentiometers 62 and the succeeding board is simultaneously conveyed on the conveyor 36 and reaches the position to be scanned. The carrier 46 travels again to scan the marked face of the board while the potentiometers 62' are operative to memorize the locations of the markings detected by the photo-electric elements 46b on the carrier 46. Upon completion of the cutting operation on the preceding board, the saw blades of the sawing unit are shifted to positions selected in accordance with the signal voltages from the potentiometers 62'. The two sets of potentiometers 62 and 62' are in this manner alternately put into operation so that the loss in the performance efficiency otherwise resulting from the downtime period of the signal generating units can be eliminated.

A preferred example of the electric circuits adapted to control the saw blade shifting mechanism of the saw apparatus above described is illustrated in FIGS. 9a and 9b. The control circuit herein shown is specifically arranged for use with the signal generator unit shown in FIG. 1 for simplicity of description. It is, however, apparent that the principle of operation of the shown control circuit is applicable to the signal generator unit of the construction shown in FIG. 8 which minor modification.

Referring to FIG. 9a, the signal generator unit 56 has four (or a suitable number of) potentiometers 62a to 62d which are connected in parallel to a source of power. The potentiometers 62a and 62d are connected to a clutch control circuit 312 through respective clutches 66. The clutch control circuit 312 comprises flip-flop circuits 314a to 314d connected to the clutches for the associated potentiometers 62a to 62d through drivers 3160 to 316d, respectively. The flipflop circuits 314a to 314d have set terminals connected to a suitable logical circuit such as an AND-gate circuit 310. This AND-gate circuit 310 has one input terminal connected to the limit switch 44 (FIG. 1), and the other input terminal is energized when the saw-blade shifting operation is complete. The reset terminals of the Hipflop circuits 3140 to 314d are connected to output terminals of a shift register 318 having an input terminal connected to a suitable logical circuit such as an AND- gate circuit 320. The AND-gate circuit 320 has one input terminal connected to the photo-electric elements 46b on the carrier 46 (FIG. 1) through an amplifier 322, and the other input terminal is energized when the carrier 46 is being moved forward. Turning to FIG. 9b, the potentiometer 62 which may be any one of those designated by reference numerals 62a to 62d has a wiper arm 324. This mark-position indicating potentiometer 62 is connected in parallel with the associated blade-position indicating potentiometer 158 having a wiper arm 326 to the comparator 160 which was also previously mentioned. THe comparator 160 is connected to a switch control unit 328 through lines 330 and 330. The solenoid operated valve 146 (see FIG. 1) has solenoid coils 146a and 1461) for actuating the valve member. The solenoid coil 1460 is connected to a power source 332 through a line 334 and a relay switch 336 which is controlled from the switch control unit 328 through a line 338. The solenoid coil 146b, on the other hand, is connected to a power source 340 through a line 342 and a relay switch 344 which is controlled from the switch control unit 328 through a line 346. The switch control unit 328 is responsive to the limit switch 70 which, in turn, is responsive to the movement of the carrier 46 (FIG. 1 over its full stroke. This switch control unit 328 may be connected to the AND-gate circuit 310 for supplying thereto a signal indicative of the completion of the blade shifting operation. The solenoid operated valve 146 communicates with the hydraulic cylinder 144 for moving the shifter 128 (FIG. 2) through fluid lines 348 and 350. The piston rod 142 of the hydraulic cylinder 144 is connected to the shaft 154 of the potentiometer 158 (see FIG. 2).

The wiper arm 324 of the mark-position indicating potentiometer 62 is normally set to a zero-position which is indicated at 63 in FIG. 9b. When the limit switch 44 (FIG. 1) is closed upon engagement with the board and if the saw blades are all at rest, the set signals are fed to the flip-flop circuits 3140 to 314d through the AND-gate circuit 316 whereupon the solenoid operated clutches 66 of the mark-position indicating potentiometers 62a to 620' are coupled by the driver circuits 3160 to 316d, respectively. The wiper arms of the potentiometers 62a to 620' are thus turned through angles which are proportional to the distances traveled by the carrier 46 (FIG. 1). As the carrier advances, the

photoelectric elements 46h carried thereon detect the markings on the board so that the AND-gate circuit 320 issues reset signals for the flip-flop circuits 314a to 314d in a sequential fashion which is regulated by the shift register 318. As the flip-flop circuits 3140 to 3l4d are thus cut off successively, the solenoid operated clutches 66 are disengaged one by one. The wiper arms of the mark-position disengaged potentiometers 62a to 62d are consequently brought to a stop as the associated clutches 66 are disengaged. Upon completion of the scanning operation, the limit switch 70 becomes operative to actuate the switch control unit 328 subsequent to the comparator 160. This comparator I60 receives signal voltages from the mark-position and blade-position indicating potentiometers 62 and 158 and compares the voltages with each other to produce a control signal determined by the difference between the voltages. If the signal voltage from the potentiometer 62 is lower than the voltage from the potentiometer 158, then the comparator [60 supplies a control signal to the switch control unit 328 through the line 330 to energize the relay switch 336 through the line 338. The relay switch 336 is therefore closed so that the solenoid operated valve 146 causes the piston rod 142 to move outward of the cylinder 144 until the signal voltage from the potentiometer I58 equals the voltage from the potentiometer 62. The saw blade associated with the potentiometer I58 is accordingly shifted to a position dictated by the signal voltage from potentiometer 62. When, conversely, the signal voltage from the potentiometer 62 is higher than the voltage from the potentiometer I58, then a control signal is transmitted from the comparator through the line 330' to the switch control unit 328 to close the relay switch 344 through the line 346 for causing the valve 146 to withdraw the piston rod 142 until the wiper arm 326 of the potentiometer 158 is synchronized with the wiper arm 324 of the potentiometer 62. In the absence of a difference between the voltages from the potentiometers 62 and 158, the switch control unit 328 is opera tive to keep the relay switches 336 and 344 open so that the piston rod [42 and the associated saw blade are held stationary. Upon completion of the saw blade shifting operation, the difference between the input voltages to the comparator I60 becomes zero so that the switch control unit 328 transmits a signal to the AND-gate circuit 3") which in turn supplies the set signal to the flip-flop circuits 314a to 314d for the subsequent cycle of scanning and blade shifting operations.

The above described circuit arrangement is merely illustrative, and it is apparent that the signal controlling the saw-blade shifting operation may be obtained in any other desired manner in accordance with the mark ings on the board to be cut is.

What is claimed is:

l. A saw apparatus for cutting a board into sections in accordance with at least one marking applied thereto, comprising at least one blade conveying means for conveying the marked board in a predetermined path which is aligned with said at least one saw blade, scanning means operable to detect said at least one marking on the board, signal generating means responsive to said scanning means for producing a signal representative of the location of said at least one marking. and saw-blade shifting means responsive to said signal for axially moving said at least one saw blade to a position aligned with said marking.

2. A saw apparatus as set forth in claim 1, in which said scanning means comprises a carrier which is movable over said path for scanning the marked board, a source of light for irradiating said marked board and a plurality of photo-electric elements operable to produce a signal voltage upon sensing said at least one marking on the board.

3. A saw apparatus as set forth in claim I, in which said signal generating means comprises mark-position indicating signal generating means responsive to said scanning means, a blade-position indicating signal generating means responsive to said saw-blade shifting means and comparing means for comparing the signals from said mark-position and blade position indicating signal generating means and producing a control signal for causing said saw-blade shifting means to move said at least one saw blade to a position in which said signals are equalized.

4. A saw apparatus as set forth in claim 2, in which said signal generating means comprises gearing means movable responsive to the movement of said carrier, at least one mark-position indicating potentiometer responsive to the motion of the bearing means for producing a signal voltage proportional to the distance of movement of said carrier over said path, means for dis connecting said potentiometer from said gearing means when said at least one marking on the board is detected by said scanning means, at least one blade-position indicating potentiometer responsive to the axial movement of said at least one saw blade on said rotary shaft for producing a signal voltage indicative of the position of the saw blade on the shaft, and comparing means for comparing the signal voltages from said mark-position and blade-position indicating potentiometers and producing a control signal for causing said saw-blade shifting means to move said at least one saw blade to a position in which said signals from said mark'position and blade-position indicating potentiometers are equal to each other.

5. A saw apparatus as set forth in claim 1, in which said conveying means comprises a conveyor traveling below said at least one saw blade in a direction transverse to said rotary shaft, and pressing means positioned adjacent said conveyor and said at least one saw blade for pressing the board to be cut and cut sections of the board upon said conveyor.

6. A saw apparatus as set forth in claim 5, in which said pressing means comprises a plurality of rollers positioned ahead of and behind said at least one saw blade in said path and spring means biasing said rollers toward said conveyor.

7. A saw apparatus as set forth in claim 6, wherein the rollers positioned behind said at least one saw blade include a first set of rollers and a second set of rollers, the rollers of each set being mounted for rotation about respective parallel axes transverse to said path in axially spaced relationship, the two axially terminal portions of a roller in each set being axially coextensive with respective axially terminal portions of two rollers in the other set.

8. A saw apparatus as set forth in claim 6, in which said conveying means further comprises returnpreventive means positioned ahead of said at least one saw blade for preventing rearward movement of the board conveyed to said saw blade.

9. A saw apparatus as set forth in claim 1, in which said saw-blade shifting means includes saw-blade guid- 

1. A saw apparatus for cutting a board into sections in accordance with at least one marking applied thereto, comprising at least one blade conveying means for conveying the marked board in a predetermined path which is aligned with said at least one saw blade, scanning means operable to detect said at least one marking on the board, signal generating means responsive to said scanning means for producing a signal representative of the location of said at least one marking, and saw-blade shifting means responsive to said signal for axially moving said at least one saw blade to a position aligned with said marking.
 2. A saw apparatus as set forth in claim 1, in which said scanning means comprises a carrier which is movable over said path for scanning the marked board, a source of light for irradiating said marked board and a plurality of photo-electric elements operable to produce a signal voltage upon sensing said at least one marking on the board.
 3. A saw apparatus as set forth in claim 1, in which said signal generating means comprises mark-position indicating signal generating means responsive to said scanning means, a blade-position indicating signal generating means responsive to said saw-blade shifting means and comparing means for comparing the signals from said mark-position and blade position indicating signal generating means and producing a control signal for causing said saw-blade shifting means to move said at least one saw blade to a position in which said signals are equalized.
 4. A saw apparatus as set forth in claim 2, in which said signal generating means comprises gearing means movable responsive to the movement of said carrier, at least one mark-position indicating potentiometer responsive to the motion of the bearing means for producing a signal voltage proportional to the distance of movement of said carrier over said path, means for disconnecting said potentiometer from said gearing means when said at least one marking on the board is detected by said scanning means, at least one blade-position indicating potentiometer responsive to the axial movement of said at least one saw blade on said rotary shaft for producing a signal voltage indicative of the position of the saw blade on the shaft, and comparing means for comparing the signal voltages from said mark-position and blade-position indicating potentiometers and producing a control signal for causing said saw-blade shifting means to move said at least one saw blade to a position in which said signals from said mark-position and blade-position indicating potentiometers are equal to each other.
 5. A saw apparatus as set forth in claim 1, in which said conveying means comprises a conveyor traveling below said at least One saw blade in a direction transverse to said rotary shaft, and pressing means positioned adjacent said conveyor and said at least one saw blade for pressing the board to be cut and cut sections of the board upon said conveyor.
 6. A saw apparatus as set forth in claim 5, in which said pressing means comprises a plurality of rollers positioned ahead of and behind said at least one saw blade in said path and spring means biasing said rollers toward said conveyor.
 7. A saw apparatus as set forth in claim 6, wherein the rollers positioned behind said at least one saw blade include a first set of rollers and a second set of rollers, the rollers of each set being mounted for rotation about respective parallel axes transverse to said path in axially spaced relationship, the two axially terminal portions of a roller in each set being axially coextensive with respective axially terminal portions of two rollers in the other set.
 8. A saw apparatus as set forth in claim 6, in which said conveying means further comprises return-preventive means positioned ahead of said at least one saw blade for preventing rearward movement of the board conveyed to said saw blade.
 9. A saw apparatus as set forth in claim 1, in which said saw-blade shifting means includes saw-blade guiding means for guiding said at least one saw blade on said rotary shaft when said saw blade is moved axially thereon.
 10. A saw apparatus as set forth in claim 1, further comprising saw-blade position indicating means cooperating with said saw-blade shifting means for visually indicating the axial position of said at least one saw blade.
 11. A saw apparatus as set forth in claim 1, in which said scanning means includes stop means for temporarily holding said marked board at a standstill adjacent said scanning means when the scanning means is operative to scan the board.
 12. A saw apparatus for cutting a board into sections in accordance with at least one marking applied thereto, comprising at least one movable saw blade, conveying means for conveying the marked board in a predetermined path, scanning means operable to detect said at least one marking on the board, signal generating means responsive to said scanning means for producing a signal representative of the location of said at least one marking, and saw-blade shifting means responsive to said signal for moving said at least one saw blade to a position which is substantially aligned with said marking in said path for cutting engagement with the conveyed board.
 13. A saw apparatus for cutting a board into sections in accordance with at least one marking applied thereto, comprising at least one saw blade movable between a plurality of positions, first signal generating means for producing a first signal representative of the location of said at least one marking on the board, second signal generating means for producing a second signal representative of the instantaneous position of said saw blade, comparing means for comparing said first and second signals and for producing a third signal which is representative of the distance between said location of the marking and said instantaneous position of the saw blade, and saw-blade shifting means responsive to said third signal for moving said saw blade from said instantaneous position toward another position thereof nearer said marking.
 14. A saw apparatus for cutting a board into sections comprising a shaft having an axis and mounted for rotation about said axis; at least one circular saw blade mounted on said shaft for rotation therewith and for axial movement relative to said shaft; conveying means for conveying said board past said blade in a path transverse to said axis, said conveying means including a conveyor traveling below said shaft for cutting of a board carried by said conveyor into a plurality of sections by said at least one saw blade, and pressing means spacedly above said conveyor and adjacent said at least one saw blade for pressing said sections downwardly upon said conveyor, said pressing means including a plurality of first sets of rollers, a plurality of second sets of rollers, the rollers of each set being mounted for rotation about respective parallel axes transverse to said path in axially spaced relationship, the two axially terminal portions of a roller in each first set being axially coextensive with respective axially terminal portions of two rollers in an adjacent one of said second sets, and spring means biasing said rollers toward said conveyor. 